Current olefin (ethylene, propylene, and 1,3-butadiene) are made by cracking hydrocarbon feeds ranging from LPG to light naphtha in very large thermal steam crackers. In addition, the conversion yield and selectivity for both propylene and ethylene are poor using the current steam cracking procedure in addition to the following problems with large cracking plants.
There are three drawbacks to large crackers. First, to be competitive, they need to produce at least a 1 billion pounds/year of ethylene. The cost of building units this large is about one dollar for each lb/year of ethylene produced or about 1 billion dollars/unit. Second, while there is some flexibility in the product output based on feed and operating conditions, this is rather limited and these units invariably produce one or more low value products(s) that the operators would rather not make. Third, they operate at high temperatures (800 to 1200 degrees F.) and are very energy intensive. Moreover, the thermal cracking reaction is highly endothermic (substantial energy input is required); the equilibrium conversion is thermodynamically limited and selectivity declines at higher temperatures; carbon oxide formation occurs; side reactions occur (undesired product formation) requiring extensive product purification. While a number of schemes have been proposed to couple olefin formation with further down stream products to improve efficiencies, they have not found wide-spread commercial application. Olefins (alkenes), such as ethylene (C2H4) and propylene (C3H6), are among the primary sources of starting materials for the chemical industry.
About 60 billion pounds of ethylene is produced annually in the USA. It is the starting material for polyethylene, ethylene copolymers, ethylene glycol, ethylene oxide, (surfactants and detergents), etc. There is a commercial need for process technology that provides an economical alternative for smaller units which operate with improved product output flexibility.